I have two toilets on second floor; one on the first. One of the 2nd floor toilets and the one on the first have trouble getting solid waste out of the bowls. Once it gets out of the bowls, everything is OK. I replaced the 2nd floor unit hoping to solve at least ONE problem. Bought one with a slightly larger hole at bottom of the bowl. Same problem as with old model unit on first floor.

Things I've checked: Plumber confirmed vent stack was clear when we checked it at rooftop. Pipes to the main waste stack are clear...use homemade mixture (baking soda, etc) every two months.